1. Field of the Invention
The present invention relates to a thin absorbent article such as a vaginal discharge absorbing sheet called panty liner or a urine absorbing sheet for an incontinence patient, more specifically, to the absorbent article which provides an excellent cushiony feeling even though it is sufficiently thin, and a method of manufacturing the same.
2. Description of the Related Art
As a thin absorbent article, a vaginal discharge absorbing sheet called panty liner has been widely known. Such absorbing sheet is worn by fixing it on the inner side of a crotch portion of an undergarment through a pressure sensitive adhesive. Generally, this conventional absorbing sheet has a thin absorbent layer between a liquid-impermeable backsheet and a topsheet formed from a spunlaced nonwoven fabric or the like. The absorbent layer is generally formed from a plurality of sheets of tissue paper stacked one on another, air laid pulp, or the like.
The absorbing sheet is preferred to provide the wearer with a soft feeling equivalent to that of the undergarment. Especially, since the topsheet comes into contact with the wearer""s skin, specifically the female genital organ, its contact feeling should be soft. However, in the case where the topsheet is formed from a flat nonwoven fabric such as spunlaced nonwoven fabric, it can not provide a good contact feeling. In addition, the topsheet can not provide a soft appearance when viewed by the wearer upon wearing.
In case of a relatively thick absorbent article such as a sanitary napkin, on the other hand, a good cushiony feeling can be provided to the wearer""s skin by shaping its topsheet to have ridge portions and groove portions significantly different in level. However, since the basic structure of the vaginal discharge absorbing sheet, which should be felt as a part of the undergarment in use while being fixed on the inner side of the crotch portion of the undergarment, must be significantly thin, it is substantially impossible to shape the topsheet to have ridge portions and groove portions significantly different in level.
In order to provide the wearer with a soft wearing feel equivalent to that of the undergarment as well as a soft appearance, nevertheless, it is still possible to shape the topsheet to have ridge portions and groove portions slightly different in level. However, since the absorbent layer underlying the topsheet having such ridge and groove portions is thin and relatively hard, the difference in level between the ridge and groove portions of the topsheet is removed or reduced in the manufacturing process of the thin absorbent article. Therefore, the originally expected soft feeling can not be obtained.
In addition, since the absorbent article of this kind is generally folded and wrapped so as to improve the portability by the user, the difference in level between the ridge and groove portions is also removed or reduced easily by the pressure applied in the folding and wrapping process or the pressure applied when it is stored in such wrapped state.
The present invention has been worked out in view of the shortcoming in the prior art set forth above. It is therefore an object of the present invention to provide a thin absorbent article which is capable of providing a soft contact feeling to the wearer""s skin as well as a soft appearance, and is also capable of maintaining such soft feeling.
It is another object of the present invention to provide a method of manufacturing an absorbent article which is capable of maintaining a soft feeling constantly.
According to a first aspect of the invention, there is provided an absorbent article comprising: a topsheet formed from a nonwoven fabric; a backsheet; and a cushion layer disposed between the topsheet and the backsheet, wherein
the topsheet is three-dimensionally shaped to have hills and valleys alternating with each other, the hills and the valleys being arranged at a pitch of 0.5 to 5 mm, the three-dimensionally shaped topsheet having a thickness of 0.5 to 5 mm under a condition where a pressure of 49 Pa is applied thereto,
the cushion layer, under a condition where a pressure of 49 Pa is applied thereto, has a thickness equal to or larger than the thickness of the topsheet, and
the cushion layer has a compression property value smaller than that of the topsheet.
With such construction, the difference in level between the hills and the valleys of the topsheet is hardly removed or reduced even if an external pressure is applied thereto in the manufacturing process or after wrapping. Therefore, the absorbent article can constantly provide a soft contact feeling to the skin as well as a soft appearance.
Preferably, the thickness of the cushion layer under a condition where a pressure of 49 Pa is applied thereto is one to five times the thickness of the topsheet. Within such range, the absorbent article can be made thin as a whole.
For example, the cushion layer is formed from a through-air bonded nonwoven fabric comprising thermoplastic fibers. The through-air bonded nonwoven fabric has an excellent cushioning property even if it is of the thin type, thereby effectively preventing the three-dimensionally shaped topsheet from being crushed.
It is possible that the topsheet mainly absorbs and retains a liquid and the cushion layer substantially does not have a function of retaining a liquid. Alternatively, it is also possible that the cushion layer substantially has a function of absorbing and retaining a liquid. In this case, the main body of the absorbent article may be composed of only three layers, i.e., the topsheet, the cushion layer and the backsheet. Therefore, the main body can be made thin and felt as integrated with an undergarment when fixed on the inner side of the undergarment in use.
In an alternative to the three-layer structure, it is also possible to construct the main body to have at least four layers by providing an absorbent layer having a function of absorbing and retaining a liquid between the cushion layer and the backsheet. With the absorbent layer being thus provided, the absorbent article can absorb and retain more liquid as compared with the case where the main body is composed of only three layers.
In this case, the absorbent layer may be formed from an air-laid nonwoven fabric comprising pulp. By employing the air-laid nonwoven fabric comprising pulp as the absorbent layer, the absorbent layer can absorb and retain more liquid than the cushion layer even if it is of the thin type.
Accordingly, the absorbent article of the present invention is preferably used as a vaginal discharge absorbing sheet. However, the absorbent article of the present invention is also applicable to a thin urine absorbing sheet for incontinence patients.
According to another aspect of the present invention, there is provided a method for manufacturing an absorbent article including: a topsheet formed from a nonwoven fabric; a backsheet; and a cushion layer disposed between the topsheet and the backsheet, the method comprising
applying heat to the cushion layer unwound from a material roll to restore bulkiness of the cushion layer, before laminating the topsheet, the cushion layer and the backsheet.
In the manufacturing method, even if the cushion layer is in a compressed state when supplied from the material roll, it is heated to restore the bulkiness, thereby providing a soft feeling to the manufactured absorbent article.
Preferably, the absorbent article manufacturing method further comprises cooling the cushion layer after applying heat to the cushion layer. With the cooling process, the restored bulkiness can be set immediately.
Preferably, the cushion layer is formed from a through-air bonded nonwoven fabric comprising thermoplastic fibers. Even if it is once compressed to reduce thickness, the through-air bonded nonwoven fabric comprising thermoplastic fibers can easily restore its bulkiness when heat is applied thereto.
It is also possible that the absorbent article manufacturing method further comprises disposing an absorbent layer, which has a function of absorbing and retaining a liquid, between the cushion layer and the backsheet. In this case, it is preferred that the absorbent article manufacturing method further comprises applying heat to the absorbent layer unwound from a material roll to restore bulkiness of the absorbent layer, before disposing the absorbent layer between the cushion layer and the backsheet. With the bulkiness of the absorbent layer being restored, the absorbent layer can absorb and retain more liquid. It is also preferred that the absorbent article manufacturing method further comprises cooling the absorbent layer after applying heat to the absorbent layer. With the cooling process, the restored bulkiness of the absorbent layer can also be set immediately.
For example, the absorbent layer is formed from an air-laid nonwoven fabric comprising pulp. The bulkiness of the air-laid nonwoven fabric can also be restored by applying heat thereto.
It is also preferred that the topsheet is three-dimensionally shaped to have hills and valleys alternating with each other, the hills and the valleys are arranged at a pitch of 0.5 to 5 mm, and the three-dimensionally shaped topsheet having a thickness of 0.5 to 5 mm under a condition where a pressure of 49 Pa is applied thereto. Since the bulkiness of the cushion layer is restored in the manufacturing method, the difference in level between the hills and the valleys of the topsheet can be easily prevented.